A sprayer-type faucet has a valve and an outlet head that normally sits on a faucet arm to give the device the appearance and function of a standard faucet that dispenses water when the associated valve is opened. In addition the head can be pulled from the support arm to work as a sprayer. To this end the head is connected via a flexible hose that extends back down through the arm to the valve, normally forming a loop under the deck to provide some range of movement for the spray head. Such an arrangement is extremely convenient in that it eliminates the need for a separate sprayer attachment and it allows convenient switchover from mobile spray to fixed faucet. It can be used in a standard kitchen sink, in a beauty-shop setting, and or in any type of application where a sprayer might be needed in addition to a faucet.
The primary disadvantage of such a system, as opposed to the standard nonextensible faucet, is that the spray head can be left in the sink, in fact below the surface of the water therein. If the valve is still open and there is a momentary pressure reversal, that is the supply pressure momentarily drops below atmospheric, it is therefore possible for such an arrangement to suck in water from the sink, contaminating the clean water in the supply lines. This possibility is an illegal situation that plumbing codes specifically forbid.
In commonly owned U.S. Pat. No. 5,213,268 a faucet assembly is described that has a housing formed with an inlet port, an outlet port, and a vent port and with a vent passage extending between the inlet and vent ports and a feed passage extending between the outlet port and a location in the vent passage between the inlet and vent ports. An inner valve seat is provided in the vent passage between the location and the inlet port, a vent valve seat is provided in the vent passage between the location and the vent port, and an outer valve seat is provided in the vent passage between the location and the vent seat. An inner valve body is displaceable in the vent passage between an inner end position sitting in the inner seat and blocking flow out of the vent passage through the inlet port and an outer end position sitting in the outer seat and blocking flow from the location to the vent port. Similarly an outer valve body is displaceable in the vent position between an outer end position sitting in the vent seat and blocking flow out of the vent passage through the vent port and an inner end position permitting flow through the vent port. The valve bodies are biased into the respective outer positions. A mixing valve normally feeds water under pressure to the inlet port and thereby presses the inner valve body into the outer position and, in an abnormal pressure-reversal situation, applies a subatmospheric pressure to the inlet port and thereby moves the inner valve into the inner position. A faucet arm on the housing carries a removable spray head and a hose has one end connected to the spray head and an opposite end connected to the outlet port of the housing.
Building the backflow preventer into the valve requires that the valve be fairly bulky. This is frequently undesirable from a design point of view, in particular when the fixture is to be used in a bathroom setting.
In another system described in U.S. Pat. No. 5,279,324 the fixture is provided with a coupling having a chamber, an inlet passage through which fluid may enter the chamber from a supply, an outlet passage through the fluid may exit the chamber and the coupling, and a vent passage in fluid communication with the chamber and having an inlet in communication with ambient atmosphere and an outlet in communication with the chamber. The coupling is provided between the fixture's valve and a hose-connected spray head. A vacuum-breaker check valve is located in the vent passage of the coupling and includes a valve member for closing the vent inlet when pressure in the chamber is greater than pressure at the vent inlet and for opening the vent inlet when pressure in the chamber is less than pressure at the vent inlet.
With this arrangement the check valve can fail or leak and allow backflow into the lines. Even if it is working perfectly some backflow is possible under certain circumstances in the time it takes the check valve under the counter to react.